/*$Id: shellcnv.c,v 1.15 2000/09/28 21:11:11 bsmith Exp bsmith $*/

#include "src/mat/matimpl.h"        /*I "petscmat.h" I*/
#include "src/vec/vecimpl.h"  
  
#undef __FUNC__  
#define __FUNC__ /*<a name=""></a>*/"MatConvert_Shell"
int MatConvert_Shell(Mat oldmat,MatType newtype,Mat *mat)
{
  Vec      in,out;
  int      ierr,i,M,m,*rows,start,end;
  MPI_Comm comm;
  Scalar   *array,zero = 0.0,one = 1.0;

  PetscFunctionBegin;
  PetscValidHeaderSpecific(oldmat,MAT_COOKIE);
  PetscValidPointer(mat);
  comm = oldmat->comm;

  ierr = MatGetOwnershipRange(oldmat,&start,&end);CHKERRQ(ierr);
  ierr = VecCreateMPI(comm,end-start,PETSC_DECIDE,&in);CHKERRQ(ierr);
  ierr = VecDuplicate(in,&out);CHKERRQ(ierr);
  ierr = VecGetSize(in,&M);CHKERRQ(ierr);
  ierr = VecGetLocalSize(in,&m);CHKERRQ(ierr);
  rows = (int*)PetscMalloc((m+1)*sizeof(int));CHKPTRQ(rows);
  for (i=0; i<m; i++) {rows[i] = start + i;}

  ierr = MatCreate(comm,m,M,M,M,mat);CHKERRQ(ierr);
  ierr = MatSetType(*mat,newtype);CHKERRQ(ierr);

  for (i=0; i<M; i++) {
    ierr = VecSet(&zero,in);CHKERRQ(ierr);
    ierr = VecSetValues(in,1,&i,&one,INSERT_VALUES);CHKERRQ(ierr);
    ierr = VecAssemblyBegin(in);CHKERRQ(ierr);
    ierr = VecAssemblyEnd(in);CHKERRQ(ierr);

    ierr = MatMult(oldmat,in,out);CHKERRQ(ierr);
    
    ierr = VecGetArray(out,&array);CHKERRQ(ierr);
    ierr = MatSetValues(*mat,m,rows,1,&i,array,INSERT_VALUES);CHKERRQ(ierr); 
    ierr = VecRestoreArray(out,&array);CHKERRQ(ierr);

  }
  ierr = PetscFree(rows);CHKERRQ(ierr);
  ierr = VecDestroy(in);CHKERRQ(ierr);
  ierr = VecDestroy(out);CHKERRQ(ierr);
  ierr = MatAssemblyBegin(*mat,MAT_FINAL_ASSEMBLY);CHKERRQ(ierr);
  ierr = MatAssemblyEnd(*mat,MAT_FINAL_ASSEMBLY);CHKERRQ(ierr);
  PetscFunctionReturn(0);
}